It's a variation of the "drone brood removal" or "sacrificial drone brood"
method?
 
1) Any of these require a fair amount of careful work (if the drone brood isn't
removed on time, it increases varroa production rather than decreasing it);
2) the bees put quite a bit of resources (feeding, incubation energy and space)
into a slab of drone brood raised to capping. Discarding it may seem less
harmfull than killing a couple of thousand workers, but may be just as much of a
drain;
3) 40 - 50 % reduction, according to estimates that 90 % reduction per year is
required to co-exist with varroa, would only be adequate if some other reduction
was occurring in the colonies.
 
Regardless of the theoretical problems, if it works, great! Where varroa is just
getting established, it might work for a year or too, until varroa gets to a
damage threshold. (actually, year 3 -4  of varroa establishment might be the
worst, since at that point, lots of un-managed colonies will be alive but
heavily infested, so reinfestation of managed colonies will be rapid..when the
unmanaged colonies have perished, the varroa incidence should decrease).
 Where varroa has become well established, I think a control should show a 4
year period of success, before it could be judged adequate.
 
By the way, are you aware of any recent news regarding the reports of
fluvalinate resistant varroa in northern Italy? I have 3 brief papers from '93
in Italian which I hope to have translated enough to assess, but the abstract
says "the results suggest that varroa had become resistant to fluvalinate".
(I see in one of the papers (Marletto, F. 1993. Recrudescence of varroa disease.
Apicolt. mod. 84 3 - 6.) a photo of the 3 section drone frame you describe.
 
 
Kerry Clark, Apiculture Specialist
B.C. Ministry of Agriculture
1201 103 Ave
Dawson Creek B.C.
        V1G 4J2  CANADA          Tel (604) 784-2225     fax (604) 784-2299
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